1. Field of the Invention
The invention relates to a rotary anode X-ray tube which includes a sleeve bearing which serves to journal the rotary-anode and includes an inner bearing segment and an outer bearing segment which is provided with a holder, intermediate pieces being provided between the holder and the inner bearing segment and correspondingly formed bearing surfaces on the inner bearing segment and in the intermediate pieces being arranged to take up radial and axial bearing forces. The invention also relates to a sleeve bearing which is suitable for use in a rotary-anode X-ray tube.
2. Description of Related Art
A rotary-anode X-ray tube and a sleeve bearing of this kind are known from DE-GM 87 05 478. Therein, the outer surfaces of the intermediate pieces are adapted to the tubular holder whereas their inner surfaces are adapted to the bearing surfaces on the inner bearing segment which have the form of a truncated cone. A bias force, applied to one of the intermediate pieces and produced by a spring, ensures that the bearing clearance remains constant also when the temperature of the sleeve bearing increases; however, the starting moment is thus also increased.
The bearing capacity of a sleeve bearing is dependent particularly on the distance between the bearing faces co-operating in the inner and the outer bearing segments. The bearing capacity of the sleeve bearing is greater as this distance is smaller. In practice this distance is of the order of magnitude of 10 .mu.m. Such small distances, which should also remain constant across the bearing surfaces, can be achieved only by costly precision manufacture. In comparison with sleeve bearings which have bearing surfaces extending perpendicularly to the axis of rotation so as to take up the axial bearing forces and at least one cylindrical bearing surface for taking up the radial bearing forces, the known sleeve bearing offers the advantage that only two bearing surfaces (having the shape of a truncated cone) must be formed with the necessary precision on the inner bearing segment and in the intermediate pieces.
Moreover, however, the external surfaces of the intermediate pieces which are arranged in the tubular holder must also extend exactly concentrically with the conical bearing surfaces provided therein, because the bearing surfaces will otherwise be tilted. Finally, the outer diameter of the intermediate pieces must be very accurately adapted to the inner diameter of the tubular holder in order to ensure that on the one hand the intermediate pieces can slide in the tubular holder and that on the other hand no play remains between the facing surfaces of the intermediate pieces on the one side and the tubular holder on the other side.